U.S. patent number 3,618,878 [Application Number 04/835,513] was granted by the patent office on 1971-11-09 for aircraft throttle control.
This patent grant is currently assigned to Collins Radio Company, Lear Siegler, Inc.. Invention is credited to James A. Klein, Lowell O. Lykken, Naren M. Shah.
United States Patent |
3,618,878 |
Klein , et al. |
November 9, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
AIRCRAFT THROTTLE CONTROL
Abstract
An aircraft controlled in part during descent or ascent by
spoilers in the vertical direction, uses a throttle control signal
that is derived from the outputs of an angle of attack sensor and a
spoiler position sensor. As a result, the changes in the angle of
attack occasioned by the movement of the spoilers are compensated.
When the aircraft is held on a predetermined flight path and also
controlled in part by an elevator in the vertical direction, the
output of an elevator position sensor also contributes to the
resultant throttle control signal as a long-period anticipatory
term.
Inventors: |
Klein; James A. (Santa Monica,
CA), Lykken; Lowell O. (Westlake Village, CA), Shah;
Naren M. (Santa Monica, CA) |
Assignee: |
Lear Siegler, Inc. (Santa
Monica, CA)
Collins Radio Company (Dallas, TX)
|
Family
ID: |
25269701 |
Appl.
No.: |
04/835,513 |
Filed: |
June 23, 1969 |
Current U.S.
Class: |
244/188;
244/181 |
Current CPC
Class: |
G05D
1/0638 (20130101) |
Current International
Class: |
G05D
1/00 (20060101); G05D 1/06 (20060101); B64c
013/18 () |
Field of
Search: |
;244/77,77A,77D,42.6 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Buchler; Milton
Assistant Examiner: Forman; Jeffrey L.
Claims
What is claimed is:
1. Throttle control apparatus for an aircraft that exercises
automatic direct lift control for the vertical direction by means
of a control surface located near the center of gravity of the
aircraft, the apparatus comprising:
at least one sensor for generating a signal representative of the
actual flight of the aircraft in the vertical direction;
means responsive to the sensor signal for generating a command
signal representative of the deviation of the actual flight in the
vertical direction from a desired flight plan;
means responsive to the command signal for moving the control
surface so as to reduce the deviation;
means for producing a first signal indicative of the movement of
the control surface;
means for producing a second signal indicative of the angle of
attack of the aircraft; and
means for combining the first and second signals to produce a third
signal that is indicative of the desired throttle activity of the
aircraft.
2. Throttle control apparatus for an aircraft that has a control
surface near its center of gravity for controlling flight in a
vertical direction by direct lift, the apparatus comprising:
an aircraft throttle:
means responsive to the position of the control surface for
generating a short period damping signal that reflects the activity
of the control surface;
means for generating a control signal that reflects the deviations
of the angle of attack of the aircraft from a predetermined
value;
means for generating a long-period damping signal anticipatory of
the activity of the throttle;
means responsive to the long-period damping signal and the
short-period damping signal for modifying the control signal to
reflect changes in the lift of the aircraft brought about by the
activity of the control surface and to anticipate the activity of
the throttle; and
a throttle control device operating responsive to the modified
control signal.
3. A throttle control system for an aircraft having near its center
of gravity a control surface that controls flight of the aircraft
in a vertical direction, the system comprising:
first means for actuating the control surface, the first means
comprising at least one sensor on board the aircraft indicative of
the actual aircraft flight path, means responsive to the sensor for
generating a command signal representative of the deviation between
the actual aircraft flight path and a desired flight path in the
vertical direction, and means responsive to the control signal for
moving the control surface to reduce the deviation between the
actual and the desired flight path;
second means for sensing the movement of the control surface;
third means for sensing the angle of attack of the aircraft;
fourth means for producing an indication of a preselected angle of
attack for the aircraft;
a utilization device for throttle control of the aircraft; and
fifth means responsive to the second, third and fourth means for
controlling the utilization device.
4. The system of claim 3, in which the sensor on board the aircraft
comprises a glide slope receiver and the means for moving the
control surface maintains the aircraft on a glide slope path.
5. The system of claim 4, in which the control surface comprises
the spoilers on the wings of the aircraft.
6. The throttle control system of claim 5, in which the utilization
device comprises the throttle of the aircraft and a servo actuator
that positions the throttle responsive to the fifth means.
7. The throttle control system of claim 5, in which the utilization
device comprises an instrument that provides the pilot of the
aircraft with a sensory indication of desired throttle
activity.
8. The throttle control system of claim 5, in which sixth means are
provided for representing the normal acceleration of the aircraft,
seventh means are provided for representing the pitch attitude of
the aircraft, and the fifth means is responsive to the sixth and
seventh means in addition to the second, third, and fourth
means.
9. The throttle control system of claim 4, in which the aircraft
has substantially displaced from its center of gravity an
additional control surface that controls the flight of the aircraft
in a vertical direction, eighth means are provided for sensing the
movement of the additional control surface, and the fifth means is
responsive to the eighth means in addition to the second, third,
and fourth means.
10. The throttle control system of claim 9, in which the additional
control surface comprises an elevator at the tail of the
aircraft.
11. A method of controlling an aircraft throttle during an ascent
or descent maneuver comprising the steps of:
controlling a control surface for the vertical direction near the
center of gravity of the aircraft to maintain the aircraft on a
flight path by direct lift control;
generating a first signal representative of the difference between
the desired value of an aircraft parameter that influences proper
throttle position of the aircraft during the maneuver and the
actual value of the aircraft parameter;
generating a second, short-period damping signal representative of
the movement of the control surface of the aircraft;
generating a third, long-period damping signal anticipatory of the
throttle activity;
combining the first, second, and third signals to produce a fourth
signal; and
adjusting the position of the aircraft throttle in accordance with
the fourth signal.
12. The method claim 11, in which the first signal is generated by
generating a fifth signal representative of the desired value of
the aircraft parameter, generating a sixth signal representative of
the actual value of the aircraft parameter, and differentially
combining the fifth and sixth signals.
13. The method of claim 12, in which the desired parameter is the
angle of attack of the aircraft.
14. The method of claim 11, in which the control surface is
controlled to maintain the aircraft on a glide slope beam
transmitted from the ground.
15. A method of controlling an aircraft throttle during an ascent
or descent maneuver executed in part by direct lift control
exercised by a control surface, the method comprising the steps
of:
generating a first signal representative of the angle of attack of
the aircraft;
generating a command signal representative of the deviation between
the actual flight path during the maneuver and a desired flight
path;
controlling the aircraft in the vertical direction by moving the
control surface responsive to the control signal;
generating a second signal representative of the movement of the
control surface; and
combining the first and second signals to produce a throttle
control signal representative of the optimum angle of attack.
Description
BACKGROUND OF THE INVENTION
This invention relates to aircraft flight control and, more
particularly, to aircraft throttle control during a descent or
ascent maneuver.
In the aircraft flight control field, it is common practice to
generate a throttle control signal to assist in the control of the
throttle during ascent and descent maneuvers. Typical maneuvers of
this type used in modern commercial aviation are approach and
landing. The throttle control signal is either used as a command
signal in an automatic throttle control system or as a driving
signal for an instrument that informs the pilot how to control the
throttle manually.
During landing, the desideratum is to have the aircraft moving as
slowly as possible at touchdown without causing stall or loss of
stability prior thereto. In general, an aircraft parameter that
influences proper throttle position of the aircraft during landing
to achieve the desideratum is utilized to command the throttle.
Indicated airspeed, lift, and angle of attack are such parameters.
Assuming, for example, the utilized aircraft parameter is angle of
attack, an angle of attack selector produces a signal
representative of the desired value of angle of attack and an angle
of attack sensor produces a signal representative of the actual
value of angle of attack. The aircraft throttle is actuated
responsive to the difference between these signals, thereby
correcting the discrepancies between the desired and actual values
of angle of attack.
A signal representative of the forward acceleration of the aircraft
is commonly combined with the output of the angle of attack sensor
as a damping term that in effect anticipates and corrects for
unwanted long-period fluctuations in the actual angle of attack.
This permits more precise automatic or manual control of the
throttle position. As a rule, special measures must be taken to
eliminate the influence of the aircraft's pitch attitude on the
output of the acceleration sensor. Further, if a forward
acceleration sensor is not used on the aircraft for some other
purpose, one must be provided especially for throttle control.
Conventionally, an aircraft is controlled in the vertical direction
by adjusting the position of its elevator, which is a control
surface located at the tail of the aircraft. When the elevator is
moved away from its streamlined position, the aircraft rotates
about its pitch axis and changes its pitch attitude. Due to the
fact that the aircraft has a new pitch attitude, the indicated
airspeed and the angle of attack of the aircraft also change.
Generally, the response of an aircraft in the vertical direction to
movements of the elevator is rather slow. In some aircraft, the
control afforded by the elevator in the vertical direction is
augmented by movement of the spoilers, which are control surfaces
located on the wings of the aircraft near the center of gravity.
The response of an aircraft in the vertical direction to movements
of the spoilers is much faster than to the elevator. Since the
spoilers are located on the principal lift-producing surface of the
aircraft and are near its center of gravity, they essentially
control the flight path of the aircraft in the vertical direction
by varying the lift of the aircraft directly without an immediate
change in pitch attitude. Hence, the term that has been coined to
describe the control of an aircraft in the vertical direction by
the spoilers is "direct lift." As the aircraft is controlled in the
vertical direction by direct lift, the angle of attack changes
without affecting the indicated airspeed appreciably, so a new
angle of attack represents the desired throttle position during a
descent or ascent maneuver.
SUMMARY OF THE INVENTION
One aspect of the invention involves the generation of a throttle
control signal for an aircraft that is controlled in part by direct
lift in the vertical direction during an ascent or descent
maneuver. The changes in the angle of attack of the aircraft
occasioned by direct lift are indicated by the movement of the
spoilers. The throttle control signal for the aircraft is produced
by combining the output of an angle of attack sensor and a spoiler
position sensor. Consequently, the throttle control signal remains
essentially unaffected by the changes in angle of attack due to
direct lift control. The spoiler position sensor in effect
exercises short period corrective action on the throttle control
signal, because the response of the aircraft to spoiler movement is
fast.
Another aspect of the invention involves the production of an
anticipatory signal that damps excess throttle activity while an
aircraft is descending or ascending along a predetermined path. It
has been discovered that the movements of the elevator of the
aircraft required to hold it on the predetermined path are related
to the desired changes in throttle position for preventing aircraft
stall. In fact, the elevator movements anticipate the output of the
primary sensor, e.g., angle of attack sensor or indicated airspeed
sensor, from which the throttle control signal is derived.
Accordingly, to produce the throttle control signal, the output of
an elevator position sensor is combined with the output of the
primary sensor, which senses the actual value of the aircraft
throttle control parameter. The elevator position sensor in effect
exercises long-period corrective action on the throttle control
signal. By utilizing the output of the elevator position sensor,
which is found aboard virtually any aircraft in which the elevator
is positioned by a servo actuator, it becomes unnecessary to
provide a special sensor to generate the anticipatory signal. It
also becomes unnecessary to compensate the sensor response for the
pitch attitude of the aircraft.
BRIEF DESCRIPTION OF THE DRAWING
The features of a specific embodiment of the best mode contemplated
of carrying out the invention are illustrated in the drawing, the
single FIGURE of which is a block schematic diagram of flight
control equipment on board an aircraft.
DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENT
In the drawing are the components of part of a flight control
system located on board an aircraft. This part of the flight
control system is designed to position the throttle of the aircraft
and the control surfaces that influence the aircraft in the
vertical direction during an ascent or descent maneuver. For the
purposes of discussion, it is assumed that the aircraft is landing
at an airport that has glide slope beam-transmitting equipment.
A pitch computer 1 generates two command signals for the control
surfaces from information furnished by sensors 2. One of the
command signals from pitch computer 1 is coupled to a servo
actuator 3 that drives an aircraft elevator 4. The other command
signal from pitch computer 1 is coupled to a servo actuator 5 that
drives aircraft spoilers 6. The command signals generated by pitch
computer 1 for elevator 4 and spoilers 6 would, in general, be
related to one another, although the spoiler command signal would
be applied to servo actuator 5 through a high pass filter to limit
spoilers 6 to short period control. In some cases, the same command
signal could be used to actuate both control surfaces. Pitch
computer 1, sensors 2, and servo actuators 3 and 5 operate in a
well-known manner to position elevator 4 and spoilers 6 such that
the aircraft remains on the path of the glide slope beam. By way of
example, sensors 2 could comprise a glide slope receiver that
produces a glide slope error signal, an altimeter whose output is
differentiated to produce a vertical speed signal, and a pitch rate
gyro. Pitch computer 1 could process the information furnished by
sensors 2 in any well-known manner. Reference is made to K. C.
Kramer et al. U.S. Pat. No. 3,291,421, which issued Dec. 13, 1966,
for a suitable configuration of pitch computer 1. Another suitable
configuration of pitch computer 1 is disclosed in FIG. 2 of a
patent application entitled "Aircraft Flight Control Apparatus,"
Ser. No. 835,528, now abandoned, filed concurrently herewith in the
names of Lowell Lykken and Naren Shah.
The term "vertical direction" in this specification refers to the
direction in which the force of gravity acts. The term "elevator"
in this specification refers to a control surface for the vertical
direction which is located at the tail of the aircraft, i.e., a
substantial distance from the center of gravity of the aircraft.
Thus, when the elevator moves away from its streamlined position,
the aircraft pivots about its pitch axis and assumes a new angle of
attack. Aircraft are known in which the entire horizontal
stabilizer is pivotable as the control surface for the vertical
direction. The term "elevator" also includes such a control
surface. The term "spoilers" in this specification refers to
movable control surfaces on the wings of the aircraft, i.e.,
control surfaces near the center of gravity of the aircraft. The
spoilers on opposite wings of an aircraft are conventionally moved
in opposition to one another during a roll maneuver to improve
lateral control. In addition to this conventional use, the spoilers
are moved together in the flight control system disclosed herein
during descent and ascent maneuvers to change directly the lift
exerted on the aircraft, and thereby change the position of the
aircraft in the vertical direction. The operation of the spoilers
in this manner is referred to in this specification as "direct
lift." Partial control of the aircraft in the vertical direction is
achieved by direct lift without substantial change in the pitch
attitude of the aircraft.
The throttle control section of the flight control system operates
upon the parameter angle of attack. The term "angle of attack" in
this specification includes aircraft lift, which is directly
related to angle of attack. The output of an angle of attack
selector 10 is coupled through a summing junction 11 to one input
of a summing junction 12. The output of an angle of attack sensor
13 is coupled directly to the other input of summing junction 12,
where it is combined differentially with the output of selector 10,
as indicated by the mathematical signs in the drawing. Selector 10,
which produces a signal representative of the desired angle of
attack of the aircraft or the desired lift exerted on the aircraft,
could be a fixed signal source or a variable signal source that is
adjusted by the pilot. Alternatively, in some cases it could be a
variable signal source that is modified responsive to the dynamics
of the aircraft. Sensor 13 is a conventional sensor that produces a
signal representative of the actual angle of attack of the aircraft
or the actual lift exerted on the aircraft.
The output of summing junction 12 is coupled through a summing
junction 14 to a switch 15. The output of summing junction 14 is a
throttle control signal that can be used to control the aircraft
throttle automatically or to drive an instrument that enables the
pilot to control the throttle manually. This throttle control
signal represents in part the difference between the desired value
of the angle of attack determined by selector 10 and the actual
value of angle of attack indicated by sensor 13. When switch 15 is
in its upper position, as shown in the drawing, the throttle
control signal is coupled through a low pass filter 16 to the input
of a servo actuator 17. Low pass filter 16 serves to suppress rapid
fluctuations in the throttle control signal. Servo actuator 17
drives the aircraft throttle, which is represented by a block 18 in
the drawing. When the pilot wants to control the throttle manually,
switch 15 is placed in its lower position so the throttle control
signal is coupled to a flight director 19, which includes an
instrument providing the pilot with a visual indication of the
throttle control to be introduced.
The output of a normal accelerometer 30 is coupled to one input of
a summing junction 31, where it is combined differentially with the
output of a pitch gyro 32, as represented by the mathematical signs
in the drawing. As represented by the mathematical signs in the
drawing, the output of summing junction 31 is additively combined
with the output of summing junction 12 at summing junction 14. The
signals provided by normal accelerometer 30 and pitch gyro 32 are
anticipatory terms for the throttle control signal.
In choosing the value of angle of attack of selector 10, the prime
consideration is stall or loss of stability. In other words, the
angle of attack that results in the aircraft moving as slowly as
possible on approach and at touchdown without causing stall or loss
of stability prior thereto is the desideratum for setting selector
10. By differentially combining the outputs of selector 10 and
sensor 13, a throttle control signal is produced that represents
the deviation of the actual angle of attack from the selected value
thereof. This deviation does not truly indicate the proper throttle
activity, however, because the direct lift control exercised by
spoilers 6 changes the angle of attack of the aircraft without
immediately affecting the indicated airspeed. A spoiler position
sensor 40, which could be a preexisting component in the servo loop
that positions spoilers 6, produces a signal that represents the
movement of spoilers 6. The output of sensor 40 is coupled through
a high pass filter 41 to one input of summing junction 11, where it
is differentially combined with the output of selector 10, as
illustrated by the mathematical signs in the drawing. The function
of high pass filter 41 is to eliminate drift and long period
effects. Since the positional changes of spoilers 6 represent the
direct lift control exercised on the aircraft, the output of sensor
40 modifies the output of selector 10 to reflect changes in the
angle of attack attributable to direct lift control. The aircraft
responds quickly in the vertical direction to the spoiler
movements. This response is controlled by providing the spoilers
with rather limited authority and by high pass filtering the
spoiler command signal, as described above. Thus, spoiler position
sensor 40 provides short period damping that corrects the adverse
effects of direct lift on the throttle control signal.
In the past, a signal representative of forward acceleration of the
aircraft, has been employed as a long-period anticipatory term in
forming a throttle control signal. It has now been discovered that
the changes in position of elevator 4 are related to the desired
changes in position of the aircraft throttle, and specifically that
these changes are anticipatory of the desired throttle position.
This relationship exists because there is cross coupling between
the throttle control and the elevator surface control that is
required to maintain the aircraft on the glide slope path during
landing. In other words, as the elevator control surface is
positioned so as to maintain the aircraft on the glide slope path,
the throttle position required to maintain the optimum angle of
attack, i.e., to prevent stall, also changes. For example, assuming
an atmospheric disturbance momentarily raises the aircraft above
the center of the glide slope beam, pitch computer 1 reacts by
commanding elevator 4 to pitch the aircraft down toward beam
center. As the aircraft gradually responds to this pitch down
command, the angle of attack is reduced. Accordingly, due to the
response time of the aircraft, the pitch command and, therefore,
the elevator movement, anticipates this reduction in the angle of
attack, and causes the throttle to retard, thereby counteracting
the increase in indicated airspeed attributable to the reduced
angle of attack. An elevator position sensor 42 produces a signal
that represents the position of elevator 4. Sensor 42 could be a
preexisting component in the servo control loop that positions
elevator 4. To provide anticipation for the development of the
throttle control signal, the output of elevator position sensor 42
is coupled through a high pass filter 43, to one input of summing
junction 14, where it is differentially combined with the outputs
of summing junctions 12 and 31, as illustrated by the mathematical
signs in the drawing. The function of high pass filter 43 is also
to eliminate drift and additionally to eliminate the steady state
trimmed elevator position. It is to be noted that this aspect of
the invention is applicable to throttle control based on other
parameters than angle of attack. For example, the output of the
elevator position sensor could be used as an anticipatory signal to
modify the output of an indicated airspeed sensor.
Since the aircraft responds slowly to movements of elevator 4,
elevator position sensor 42 exercises long-period corrective action
on the throttle control signal. In other words, the anticipatory
movements of elevator 4 are employed to damp or suppress potential
long-period changes in the actual angle of attack of the aircraft.
In general, the spoiler position sensor would not be suitable as an
anticipatory term because it represents too short a period, and, if
a trim tab surface were provided on the aircraft, its position
sensor would not be suitable as an anticipatory term because in
general it represents too long a period. However, in theory it is
the output of pitch computer 1 that actually anticipates the
desired throttle position, so depending on the circumstances, and
control surface sensor that the vertical direction can possibly be
used.
The elevator positional information can also be used for
long-period damping of the throttle control signal as described
above during any ascent or descent maneuver. This aspect of the
invention is not limited to aircraft flight along a glide slope
beam or even a predetermined path. For example, the elevator
positional information anticipates the desired throttle activity
while the pilot is making an unassisted approach or landing along a
path determined by the pilot visually as he flies.
In the drawing, four separate summing junctions are shown for the
purposes of illustrating the functions of the various signals that
are combined to form the throttle control signal. In fact, all four
summing junctions could be replaced by a single summing junction
where all the signals are combined or by several summing junctions
where different combinations of signals are combined than
shown.
Although the invention has been described in the context of a
landing maneuver, the principles thereof apply to the control of
the aircraft throttle during ascent and descent maneuvers
generally, e.g., go-around after an abortive landing attempt.
* * * * *